var randomcase=new Array()
var temp = 000;
var i = 0;

for (i; i < 30; i++){
 temp = temp + 1;
 randomcase[i]=temp;
}

getCaseStudy = randomcase[Math.floor(Math.random()*randomcase.length)]

document.write('<img src="images/banners/');
document.write(getCaseStudy);
document.write('.jpg" width="425" height="75" border="0">');